Pro-collagenase-1 (matrix metalloproteinase-1) binds the alpha(2)beta(1) integrin upon release from keratinocytes migrating on type I collagen

In injured skin, collagenase-1 (matrix metalloproteinase-1 (MMP-1)) is indu ced in migrating keratinocytes. This site-specific expression is regulated by binding of the alpha (2)beta (1) integrin with dermal type I collagen, a nd the catalytic activity of MMP-1 is required for keratinocyte migration. Because of this functional association among substrate/ligand, receptor, an d proteinase, we assessed whether the integrin also directs the compartment alization of MMP-1 to its matrix target. Indeed, pro-MMP-1 co-localized to sites of alpha (2)beta (1) contacts in migrating keratinocytes. Furthermore , pro-MMP-1 co-immunoprecipitated with alpha (2)beta (1) from keratinocytes , and alpha (2)beta (1) co-immunoprecipitated with pro-MMP-1. No other MMPs bound alpha (2)beta (1) and no other integrins interacted with MMP-1. Pro- MMP-1 also provided a substrate for alpha (2)beta (1)-dependent adhesion of platelets. Complex formation on keratinocytes was most efficient on native type I collagen and reduced or ablated on denatured or cleaved collagen. C ompetition studies suggested that the alpha (2) I domain interacts with the linker and hemopexin domains of pro-MMP-1, not with the pro-domain. These data indicate that the interaction of pro-MMP-1 with alpha (2)beta (1) conf ines this proteinase to points of cell contact with collagen and that the t ernary complex of integrin, enzyme, and substrate function together to driv e and regulate keratinocyte migration.